Writing ink containing nonanoic acid

ABSTRACT

A thin writing ink having a viscosity not exceeding 50 centipoises at 25* C. comprising a dispersion of a pigment in a molecular associated liquid vehicle wherein the total solids in said ink are between about 0.05% and 35% by weight.

United States Patent [1 1 Dyson Dec. 18, 1973 WRITING INK CONTAINING NONANOIC ACID [75] Inventor:

[73] Assignee: The ParkervPen Company,

Janesville, Wis.

[22] Filed: June 7, 1971 [21] Appl. N0.: 150,783

John J. Dyson, .lanesville, Wis.

[52] US. Cl. 106/27, 106/243, 106/308 F [51] Int. Cl.. CO9d 11/00, CO9d 11/02, CO9d 11/16 [58] Field of Search 106/19-32, 243, 308 F [56] References Cited UNITED STATES PATENTS 2/1972 Zabiak 106/20 7/1954 Leekley et al. 106/24 Primary Examiner-Joseph L. Schofer Assistant Examiner-.1. B. Evans Attorney-Fidler, Patnaude, Lazo & Batz [5 7] ABSTRACT A thin writing ink having a viscosity not exceeding 50 centipoises at 25 C. comprising a dispersion of a pigmentin a molecular associated liquid vehicle wherein the total solids in said ink are between about 0.05% and 35% by weight.

7 Claims No Drawings 1 WRITING INKCONTA'INING NONANOIC ACID This invention relates to writin'giiinks and more par'-- ticularly to low viscosity writing inksthat in'clude'a'dis persed pigment a's 'a coloring; agent.

In thepast, water has served-as the vehicle in some inks that utilize either a'dispersed-pigment or-a water soluble dye to provide:the-'color; -'l heseinks have a disadvantage in thatth'ey dry rapidly on-thenib" and in the feed mechanism of a conventional pen or'ini-the pores of a felt writer', tending to plugithe'writing tipand' to prevent further passage of the. ink.

To avoid some of the disadvantages ofaque'ousinks, organic vehicles have been used with pigments and with dyes. These inks generally donotvdry by'evap'ora tionas rapidly asaqueous inks but have another disadvantage in that they cause staining; and strike-through onto'the' back of the" web b'ecausethey have-too-high' a paper penetrating ability.

It is-known that a molecular associated liquidsuch as formamidc can b'e'used asthe principal vehicle forg'dyes to provide arapid drying; and relatively.nonevaporating' and nonpen'etrating inks'lhese inks have proved to be satisfactory but have a disadvantagein that the ink: is drawn from an exposedpen pointinto clothto a larger degree than desirable; Because: of this disadvantage, there is somedanger that ink will bedrawnfrom a'pen carried in a pocket and stain a garment. in addition, such inks often exhibit.a:highidegree offeatheringiandi a low nibbability factoLFeathering isthe creationofia rough edge on a line; Thus, low'featheringis acharacteristic of inks that is continually sought. Nibbabilit'y is a measure of the rate: of flow of the: ink the given. writing system and is-obtained'by dividingathe rneteredflow rate of the ink by the negative-static fluid pressure at the writing surface when the ink linewill dry} to a non. blocking condition in. a given: time". Such static pressure tends to hold back the ink within the reservoir; High absolute, values fornibbabilit'y is generally desirable in writing inks for nib pens.

Accordingly, it is an object of this invention to provide an improved thin writing ink.

It is a further object of this invention to provide afast drying, low viscosity ink having low feathering and good nibbability, that is not easily drawn from the exposed point of a writing instrument by cloth.

It is a still further object of this invention to provide a fast drying, low viscosity writing ink that is not easily drawn from the exposed point of a writing instrument by cloth.

In accordance with the above and further objects of the invention, a rapid drying, low viscosity ink comprises a pigment dispersed in a molecular associated liquid vehicle wherein the total solids in said ink are between about 0.05% and 35% byweight, said ink having a viscosity not exceeding 50 centi'poises at 25 C. In accordance with this invention the liquid vehicle can be I. a molecular associated liquid selected from the class consisting of: g

a. glycols selected from the class consisting of ethylene glycol, diethylene glycol, triethylene glycol, hexylene glycol and mixtures thereof;

b. cyclic compounds selected from the class consisting of butyrolactone, methyl pyrrolidone, 2- pyrrolidone and mixtures thereof;

c. propylene carbonate;

d. N-Z-hydroxyethylformamide; and

e. mixtures of (a), (b), (c) and (d) liquids;

I15 amixture containing by weight 65-99.) percent of said molecular associated liquid, 0-5: percent of nonanoicfacidand 0 30 percent'of'water; or

III; a mixture'containing by weight65-97'percent of formamide, 0-5 percent of nonanoic, acid and 0-30 percent of water.

Allof. the fluids listed are. completely miscible in any combination with two exceptions, namely water, which will not mix with nonanoic acid and will not mix with "propylenecarbonate containing up to 5% nonanoic acid. When used with the other fluids propylene carbonaterwilltolerate water upto 30% of the fluidweight.

Such'an'ink including. a low vapor-pressure. molecularassociated liquid as a vehicle'f'or a dispersion of pigment'has severaladvantages. First, the ink is not drawn easily from an exposed pen point into the cloth of a pocket because the: pigments form a dam around the edge of the pen to'holdthe ink in the pointwhen it is stationary. However, whenthepen is writing, these pigment dams arebrokenwby. the motion ofthe pen so that the-ink flows freely. Another advantage is that there is areduced feathering of lines drawn with this ink. It is believed that. the dispersion of pigments forms preferentialassociations with the, sizing of the paper along the edges of the linetoprevent the ink at these points from reaching the web.

Stillfanother advantage is that theink of the present inventionhasagreater'nibbability. The reasons for this advantagerwhen a dispersion of pigments is used with a low vapor pressure molecular associated liquid as a vehicle are. not known although it is known that the nibbability is related to the viscosity and surface tension relationships and that these relationships are affected by hydrogen bonding and molecular weight considerations.

DESCRIPTION OF THE VEHICLE As used herein, a low vapor-pressure liquid is a liquid having a vapor-pressure substantially lower than that of water, such as between 0 and 40 millimeters of mercury at C.

More specifically, molecular associated liquids such as those used as the vehicle in the invention comprise moleculesin which an atom of hydrogen is attracted by strong forces to two atoms, instead of to only one atom so-that it may be considered to be acting as a bond between the two atoms. Accordingly, molecular associated liquids are those which contain relatively complex molecular species formed by the linking together of'a relatively large, but indefinite, number of single molecules by hydrogen bonds.

The vehicle,.besidesbeing a molecular associated liquid, is a liquid having a vapor pressure substantially lower than that of water. Vehicles having vapor pressures within the rangeof from 0 millimeters of mercury to 40 millimeters of niercury at 70 C. are suitable.

Suitable vehicles in accordance with this invention are ethylene glycol, diethylene glycol, triethylene glycol, hexylene glycol, butyrolactone, N-methyl-2- pyrrolidone, 2-pyrrolidone, propylene carbonate, N-2-hydroxyethylformamide and mixtures of these. Mixtures of one or more of the above liquids with up to 5% nonanoic acid and/or up to 30% water, based upon the total weight of the mixed liquids can also be employed. Another suitable vehicle is a mixture containing 65-97 percent formamide 0-5 percent nonanoic acid and 0-30 percent water.

DESCRIPTION OF THE PIGMENT Broadly, any of the commonly available pigments, both inorganic and organic including natural as well as synthetic chemical substances, can be used to form the pigment dispersions of the improved ink of the present invention. Such pigments, however, must be insoluble in the vehicle. Suitable pigments include:

Reds

Inorganic Organic iron oxide reds toluidine red cadmium reds para red English vermilion chlorinated para red copper ferrocyanide lithol red red lead Oranges Inorganic Organic ch romc orange ortho-nitraniline orange molybdatc orange dinitraniline orange orange mineral orange lakes Yellows Inorganic Organic chrome yellows Hansa yellow zinc yellow nickel azo yellow cadmium yellow yellow lakes Greens Inorganic Organic chrome green phosphotungstic green chrome oxide green phosphomolybdic green phthalocyanine green Blues Inorganic Organic I iron blues indanthrone blue ultramarine blue phthalocyanine blue Black Inorganic Organic carbon black Logwood black lamp black Nigrosine black manganese dioxide black iron oxide molybdenum sulfide White Inorganic white lead zinc oxide antimony trioxide titanium dioxide Metallic Inorganic aluminum copper bronze gold magnetic flux particles In addition, the water insoluble organic dyes known as pigment colors can be employed. Other suitable pigments are sold under the name of Pigment Fast Blue B Pigmosol, Pigment Fast Green GN Pigmosol, Carbon Black 3 Pigmosol, Lithol Fast Scarlet BBN Pigmosol, and Lithol Fast Yellow NCR Pigmosol. These pigments are manufactured and sold by Badische Anilin & Soda Fabrik A.G. (BASF Color & Chemical Company) of Paramus, New Jersey 07652. Fluorescent and phosphorescent pigments can also be employed. Suitable examples are Helicon phosphorescent Color No. 2480 manufactured by United States Radium Corporation and T-l3 Rocket Red and -17 Saturn Yellow, manufactured by Schutze Brothers Day Glo Division, Cleveland, Ohio. It is understood that various mixtures of any of the pigments listed above can be utilized in the inks of the present invention. In addition, any of the above pigments can be mixed with colorless pigments such as silicon dioxide or aluminum oxide where desired. The silicon dioxide and aluminum oxide may be either naturally hydrophilic or suitably treated to make them hydrophobic.

Approximately 35% by weight of the pigment tends to be the maximum upper limit for use in the inks. Above this upper limit, the ink solution is generally too viscous for use in instruments designed to dispense true fluids. However, it is possible to use the ink in a ball point pen. Accordingly, the inks of the present invention comprise in the range of 65-9995 percent by weight of the molecular associated liquid or solution and in the range of 005-35 percent by weight of the pigment.

The draftman's ruling pen is a practical device for determining a preferred upper limit for the pigment concentration. In such pens, the nib acts as its own capillary reservoir and flow problems at the upper limits of viscosities are generally reduced because of the nibs simple nature. Using this test, approximately 0.05-35 percent by weight of pigment appears to represent the preferred range for the molecular associated liquid based ink. Above this composition, the ink is generally too viscous to be delivered freely from the nib.

In conventional fountain pen nibs, with the complexities of reservoir and feed systems to be faced, much lower viscosities are used. For such inks, the optimum viscosities occur at total solids contents below 15 percent and might be reduced to as low as 4% or even 1% by weight in some cases.

ADDITIVES If desired, one can optionally use in the basic ink formulation conventional additives such as evaporation inhibitors, polysited hydrogen bonding molecules, diluents, hygroscopic agents, thixotropy improvers, surfactants, stabilizers and the like which can be added to improve specific properties of the ink such as paper penetrating ability, evaporation rate, surface tension, viscosity, feather control, damming effect, solvent to pigment association and cloth exclusion. These additives may be added to the vehicle or the pigment prior to mixing.

While molecular-associated liquids having a pigment as the coloring agent do not penetrate sized webs to any appreciable extent, it has also been found that the paper penetrating ability of such liquids can be decreased still further by including polysited hydrogen bonding molecules in the ink. The evaporation rate or drying rate of the molecular-associated liquid based inks can be controlled further through the use of minor amounts of essentially non-evaporating additives which promote delivery of ink from the end of a nib with properly starved lines having flat cross-sectional shapes because delivery is dominated by surface tension. The importance of non-evaporating additives results from the relationship that exists between surface tension. and viscosity of the vehicle. If the surface tension is stronger than the viscosity, so that the surface tension dominates the flow properties of the vehicle, less ink is delivered from a nib to the paper during writing. Less evaporation to reach dryness is required as a result of the lesser quantity of ink and a wider choice of liquids may be had by virtue of the control on the line volume obtained.

If it becomes necessary to dilute the ink composition, for example to reduce the viscosity, it is desirable to reduce the surface tension as little as possible. This is best accomplished by selecting the diluent according to these principles of hydrogen bonding and keeping their molecules as small and as heavy as possible.

One of the important features offered by an ink that includes a pigment dispersed in a molecular-associated liquid is a new convenience in writing. This goal is met by the production of essentially non-volatile liquids that do not evaporate as quickly as water and therefore do not dry in ink pens. On the other hand, they do dry rapidly by penetrating into paper.

To assist in the prevention of ink dry-up on the point of a pen, which can cause plugging or poor start-up, a hygroscopic agent can be added to the ink solution. Through the use of these materials, the point of the pen tends to stay moist, ready for instant writing, even if left uncovered for a considerable length of time.

The concentration of additive or additives in the finished molecular associated liquid-base inks is not critical. Different concentrations of additives can be employed depending upon the properties of the ink desired and its intended use. ln general, a minor but spe cific property-improving amount of each is utilized. Specific concentrations can vary in the range of about 0.5 to 34 percent by weight of the total weight of the ink.

Inks prepared as described above have been found to be substantially non-evaporating, properly penetrating, of relatively high surface tension, of low viscosity and capable of producing sharply defined markings on a web.

EXAMPLES The following examples are representative of different embodiments of the ink of the present invention:

EXAMPLE I Basic formulas comprising a pigment in a glycol vehicle can be prepared by adding pigment and grinding the mixture to form a dispersion of the pigment in the liquid. Generally, if the additives are employed, they are dissolved in the glycol prior to the addition of the pigment and its agitation.

( grams Ethylene glycol 60 Pigmosol Blue B 8 Ethylene glycol 42 Water 8 Pigmosol Blue B 8 Ethylene glycol 57 Nonanoic acid 3 Pigmosol Blue B 8 Ethylene glycol 32.5 Nonanoic acid 2.5 Water Pigmosol Blue B 8 Hexylcne glycol 57 Nonanoic acid 3 Pigmosol Blue B 8 Hexylenc glycol 42 Water 8 Pigmosol Blue B 8 (G) Hexylene glycol 32.5 Nonanoic acid 2.5 Water 15 Pigmosol Blue B 8 Pigmosol Blue B is a phthalocyanine pigment made by BASF.

EXAMPLE 2 An example of a black writing ink consisting essentially of a pigment dispersed in aqueous formamide has the following composition:

Formumidc 6 Water Pigmosol Carbon Black 3 (BASF) Additional examples illustrating the principles of the present invention are given below as examples 3 l6.

EXAMPLE 3 Pigment Red 7 (Cl 12420) Hexylene glycol 60 g. Blancol Conc. G.

Pigment Red 7 is an organic pigment. Blancol Concentrate Powder G. is a dispersing agent manufactured by General Analine and Film, Division of Allied Chemical & Dye Company. It is the sodium salt of sulfonated naphthaleneformaldehyde condensate and has the formula, sodium 2,2 dinaphthylmethane 6,6 disulfonate.

EXAMPLE 4 No. R-2082 black No. l (Logwood black manufactured by the Capitol EXAMPLE 7 Silica pigment (Dcgussu uncompressed fine-colorless-pigment) 0.l g. Acid blue 24 soluble dycstuff 1.0 g. Ethylene glycol 50 g.

EXAMPLE 8 An example of an ethylene glycol ink including anhydrous deliquescent agent is as follows:

Ethylene glycol g. Pigment Fast Green GN Pigmosol 10 g. Lithium chloride (Anhydrous) l.5 g.

EXAMPLE 9 An example of an ethylene glycol ink including a non-evaporating additive is as follows:

Ethylene glycol 66 g. Carbon Black 3 Pigmosol 6 g. Polyethylene glycol No.200 5.25 g.

(ave. mol. wt. 646) EXAMPLE 10 A second example of an ethylene glycol ink including a non-evaporating solvent additive follows. In this example, hydroxyethyl formamide is particularly desirable in that it does not materially'affect surface tension:

Ethylene glycol 66 g. Pigment Fast Scarlet BBN Pigmosol 6 8 Hydroxycthyl formamide ll.l g.

EXAMPLE 11 An example of an ethylene glycol ink including a non-evaporating additive and a deliquescent additive follows:

Ethylene glycol Lithol Fast Yellow NCR Pigmosol Polyethylene glycol No. 200 (ave. mol. wt. 646) Lithium chloride (Anhydrous) 3.

EXAMPLE 12 An example of an ethylene glycol ink including a non-evaporating additive and a deliquescent additive that is controlled by water addition follows:

Ethylene glycol Pigmosol Blue B Polyethylene glycol N0. 200 (ave. mol. wt. 646) Water Lithium chloride (Anhydrous) EXAMPLE 13 An example of an ethylene glycol ink that includes additional polysited hydrogen bonding molecule the normal hydrogen bonding solvent molecules of ethylene glycol and to improve their paper performance follows:

wee

Ethylene glycol 6 Pigmosol Blue B 6 g Pentaerythritol 0.4 g

EXAMPLE 14 An example of an ethylene glycol ink including pure sucrose as a hydrogen bonding agent having multiple sites follows. Here the sucrose is soluble in its pure, unesterified form, and acts as an H-bonding agent. The built-in di-functional hydrogen bonding effect of the ethylene glycol vehicle makes it a good solvent for the SUCX'OSCZ Ethylene glycol 66 g. Pigmosol Blue B 6 g. Sucrose 0.57 g.

The above formulae were all made with BASF pigmosols, as indicated, and ball milled for approximately 24 hours, and tested. They were all tested successfully for feathering and transfer to paper during writing but were significantly non-transferable to washed and dried muslin.

EXAMPLE l5 Pigmosol Blue B 8 g. propylene carbonate 60 g.

EXAMPLE l6 Pigmosol Blue B 8 g. N-2 hydroxyethyl formamide 60 g.

COMPARISON OF THE SAMPLES desired, and still have sufficient vehicle delivered to the line. This results in better cartridge life and a still faster line dry.

Colanyl pigment is Pigmosol Blue B dispersed in ethylene glycol as a thick paste.

It is to be understood that the compositions presented in the above examples are in no way limiting, the invention being limited only by the scope of the following claims:

What is claimed is:

l. A writing ink having a viscosity between about 3 to 50 centipoises at 25 C. comprising in the range of from about 0.05 to 30 percent by weight of a pigment dispersed in a liquid vehicle which is a mixture of a small amount but not more than 5 percent by weight of nonanoic acid, and 65 to 99.9 percent by weight of a liquid selected from the class consisting of:

l. Formamide and II. A molecular associated liquid selected from the class consisting of a. Glycols selected from the class consisting of ethylene glycol, diethylene glycol, triethylene glycol, hexylene glycol and mixtures thereof;

b. Cyclic compounds selected from the class consisting of butyrolaetone, methyl pyrrolidone, 2- pyrrolidone and mixtures thereof;

c. Propylene carbonate;

d. N-2-hyroxyethylformamide; and

e. Mixtures of (a), (b), (c) and (d) liquids.

2. A writing ink as set forth in claim 1 wherein said liquid vehicle contains water in a small amount but not more than 30 percent by weight of said liquid vehicle.

3. A writing ink as set forth in claim 1 in which said liquid vehicle is essentially formamide.

4. A writing ink as set forth in claim 1 in which said liquid vehicle is essentially ethylene glycol.

5. A writing ink as set forth in clain 1 wherein said pigment is a metal organic complex pigment.

6. A writing ink having a viscosity between about 3-50 centipoises at 25 C. comprising in the range of from about 0.05 to 35 percent by weight of a pigment dispersed in a liquid vehicle which is a mixture of a small amount but not more than 5 percent by weight of nonanoic acid, 0-30 percent by weight of water and 65-999 percent by weight of a molecular associated liquid selected from the class consisting of:

a. glycols selected from the class consisting of ethylene glycol, diethylene glycol, triethylene glycol, hexylene glycol and mixtures thereof;

b. cyclic compounds selected from the class consisting of butyrolactone, methyl pyrrolidone, 2- pyrrolidone and mixtures thereof;

c. propylene carbonate;

d. N-2-hydroxyethylformamide; and

e. mixtures of (a), (b), (c) and (d) liquids; said pigment being insoluble in said vehicle.

7. A writing ink having a viscosity between about 3-50 centipoises at 25C. comprising in the range of from about 0.05 to 35 percent by weight of a pigment dispersed in a liquid vehicle which is a mixture containamount but not more than 30 percent by weight of said ing by weight about 65-999 percent of formamide, mixture, said pigment being insoluble in said liquid venonanoic acid in a small amount but not more than hicle.

percent by weight of said mixture and water in a small 

2. A writing ink as set forth in claim 1 wherein said liquid vehicle contains water in a small amount but not more than 30 percent by weight of said liquid vehicle.
 3. A writing ink as set forth in claim 1 in which said liquid vehicle is essentially formamide.
 4. A writing ink as set forth in claim 1 in which said liquid vehicle is essentially ethylene glycol.
 5. A writing ink as set forth in clain 1 wherein said pigment is a metal organic complex pigment.
 6. A writing ink having a viscosity between about 3-50 centipoises at 25* C. comprising in the range of from about 0.05 to 35 percent by weight of a pigment dispersed in a liquid vehicle which is a mixture of a small amount but not more than 5 percent by weight of nonanoic acid, 0-30 percent by weight of water and 65-99.9 percent by weight of a molecular associated liquid selected from the class consisting of: a. glycols selected from the class consisting of ethylene glycol, diethylene glycol, triethylene glycol, hexylene glycol and mixtures thereof; b. cyclic compounds selected from the class consisting of butyrolactone, methyl pyrrolidone, 2-pyrrolidone and mixtures thereof; c. propylene carbonate; d. N-2-hydroxyethylformamide; and e. mixtures of (a), (b), (c) and (d) liquids; said pigment being insoluble in said vehicle.
 7. A writing ink having a viscosity between about 3-50 centipoises at 25* C. comprising in the range of from about 0.05 to 35 percent by weight of a pigment dispersed in a liquid vehicle which is a mixture containing by weight about 65-99.9 percent of formamide, nonanoic acid in a small amount but not more than 5 percent by weight of said mixture and water in a small amount but not more than 30 percent by weight of said mixture, said pigment being insoluble in said liquid vehicle. 